1. Field of the Invention
The present invention relates to a process for regenerating a catalyst that had been used for a Beckmann rearrangement reaction of cyclohexanone oxime to produce e-caprolactam. The present invention also relates to a process for producing e-caprolactam by subjecting cyclohexanone oxime to the Beckmann rearrangement reaction with the use of the catalyst thus regenerated.
2. Description of the Related Art
A process for subjecting cyclohexanone oxime to Beckmann rearrangement reaction in the presence of a zeolite catalyst is known as one of processes for producing e-caprolactam. The activity and selectivity of this catalyst usually deteriorate as the time of its use passes away to cause deterioration of the conversion of cyclohexanone oxime and the selectivity to e-caprolactam; therefore, it is proposed as a regenerating process thereof, for example, in JP-5-9180-A (corresponding to EP 0494535 A1) that the used catalyst is contacted with ammonia. Also, it is proposed in JP-2003-320260-A (corresponding to EP 1352902 A1) that the used catalyst is contacted with an aqueous solution containing a quaternary ammonium compound and/or lower alkylamines and ammonia. In addition, it is proposed in JP-2005-224752-A (corresponding to EP 1593433 A1) that the used catalyst is contacted with gas containing ammonia and/or amine, carboxylic acid and water.